In the past, a cell as shown in FIG. 1 has been used for measuring electrical conductivity of liquid having conductivity of 100 k .OMEGA..cm or less.
FIG. 1(a) shows a cell, which comprises a glass container 2 with side tubes 4 protruding inwardly on the sides thereof, electrodes 1 made of precious metal such as platinum and supported on tips of the side tubes, and lead wires 5 passed through the side tubes.
Specimen liquid 6 is placed in the container and a stopper 3 is provided to close it, and electric current is applied across the electrodes to measure electrical conductivity.
FIG. 1(b) shows a filling type cell for laboratory use. On both ends of an oblong glass container 2, electrodes 1 are disposed, and specimen liquid is filled through and discharged from two side tubes 7a and 7b extending upward. By applying electric current across the electrodes on the two ends of the glass container 2, electrical conductivity is measured.
FIG. 1(c) shows an immersion type cell. A glass container 2 has a small opening. By immersing the container in specimen liquid, the liquid enters through the opening. Electrical conductivity is measured by applying electric current across the electrodes.
However, each of the conventional type cells has a problem in corrosion resistant property, particularly against alkali, because glass is used for the container. Also, there are problems with mechanical strength and corrosion resistant property under high temperature and high pressure conditions. If metal other than precious metal is used for electrodes, problems arise with corrosion resistant property. The use of precious metal leads to the increase of cost because Pt, Au, etc. are expensive.
It is an object of the present invention to provide a cell, which has high corrosion resistant property and can be used under strong acid or strong alkaline conditions.
It is another object of the present invention to provide a cell, which has high mechanical strength and is suitable for the use under high pressure and high temperature conditions.
It is still another object of the present invention to provide a cell, which can be produced at lower cost.